Gear pairs are to be understood as the combination of any desired gears with their matching mating gears. These include, for example, worm and worm gear or also two or more mutually matching cylindrical gears or spur gears. The running properties of a toothing arrangement are determined by the shape and by dimensional deviations of the partners involved in the meshing. Measurements are therefore carried out at the produced gear with which individual kinds of deviations can be determined to evaluate the transmission behavior.
With worm gears, the check frequently takes place in the form of a rolling gear test on a separate measurement device. To check the worm wheels, they are subjected to a single-flank rolling gear test in accordance with the standards DIN 3960, VDI/VDE 2608 and VDI/VDE 2609. In this respect, the produced worm wheel is paired with its worm/test worm and the joint effect of their individual deviations on the rolling process is determined as the rolling gear deviation.
It is disadvantageous in the described process that the manufactured gears first have to be removed from the producing gear cutting machine and have to be introduced into a separate measurement apparatus. If unpermitted dimensional deviations are determined by the separate measurement apparatus, the laborious and/or expensive return of the workpiece to the gear cutting machine takes place to correct the determined deviations by a reworking.
A frequent transfer of the workpiece to be manufactured between the gear cutting machine and the measurement apparatus is in particular not acceptable in the mass production of gears. The feedback of the determined defects to the gear cutting machine also usually does not take place automatically. Possible correction steps have to be worked out independently and programmed manually at the gear cutting machine.
It is therefore the object of the present disclosure, to import a comparable measuring process into a producing gear cutting machine.
In one example, this object is achieved by a method in accordance with a method for measuring a workpiece belonging to a gear pair, wherein the method is carried out on a gear cutting machine producing the workpiece. A separate measurement apparatus is accordingly not required. The gear pair is either a worm gear with a worm wheel engaging into a worm or a cylindrical gear pair which comprises two mutually meshing cylindrical gears or spur gears.
In accordance with the method in accordance with the present disclosure according to one embodiment, in a first method step, a mating test piece mounted at the working head, in particular at the cutting head, is moved in the direction of the workpiece clamped in the workpiece mount of the machine table until the gear pair formed from the mating test piece and the workpiece is in engagement and optionally until the corresponding axial working spacing has been reached. The supply can additionally or alternatively take place by moving the tool mount in the direction of the working head.
A worm wheel located in the workpiece mount is preferably measured by a test worm mounted at the working head, in particular at the cutting head, of the gear cutting machine.
In a next method step, the clamped workpiece is driven via the drive movement of the mating test piece. The test worm rotating at the working head, for example, produces a rotational movement of the worm wheel clamped in the workpiece mount. Depending on the direction of rotation of the mating test piece, either the right hand flank or the left hand flank of the gear pair is located at the mutual engagement point. The axis of rotation of the mating test piece is optionally approximately at a right angle to the axis of rotation of the workpiece.
The respective rotational position of the workpiece to be measured is recorded over a specific period of time and is provided to a subsequent evaluation, in particular to a comparison of the workpiece rotation in relation to the test worm rotation. The recording takes place, for example, over at least one complete revolution of the test piece.
In the subsequent evaluation, the comparison of the actually detected actual position with a corresponding reference position takes place, with at least one value characterizing the rolling gear deviation of the workpiece being calculated on the basis of the comparison made. The reference position used for the comparison is known and optionally corresponds to a comparable gear pair with an almost ideal shape and dimensional deviation of the partners involved in the engagement. The determined values provide a conclusion on possible kinematic defects of the gear pair, in particular of the workpiece, under real operating circumstances.
The previously described method in accordance with the present disclosure can optionally be carried out on a gear cutting machine having a direct drive in the working head, in particular in the cutting head, and having a direct drive in the table drive. It is, however, also conceivable to carry out the method in accordance with the present disclosure on a gear cutting machine having a transmission machine table. The method in accordance with the present disclosure can be carried out equally on gear cutting machines having a vertically orientated workpiece axis or having a horizontally orientated workpiece axis.
An alternative embodiment of the method is in particular suitable for carrying out on a gear cutting machine having conventional axial drives. The assembly of the mating test piece takes place either at the working arbor, in particular the cutting arbor of the gear cutting machine, or at an additionally arranged special arbor.
Analogously to other methods described herein, the mating test piece is brought into engagement with the workpiece clamped in the workpiece mount until the corresponding axial working distance is achieved between the formed gear pair and the clamped workpiece is set into rotation by the rotational drive movement of the mating test piece.
The difference is that now instead of the actual rotational position of the workpiece, the transposition of the mating test piece relative to the workpiece is recorded and is used for the subsequent calculation of at least one value characterizing the rolling gear deviation of the workpiece. The transposition is caused by deviations in the rotational transmission between the workpiece and the mating test piece. The evaluation of the transposition serves the determining of the rolling gear deviation of the gear pair formed from the workpiece and the mating test piece. The transposition can either be measured directly or can be derived indirectly from suitable measurement variables.
A calculation of the values for the single-flank rolling gear test optionally takes place on the basis of the recorded transposition of the mating test piece relative to the workpiece in conjunction with the known gear ratio of the gear pair.
The method presented is in particular suitable for gear cutting machines which comprise a large machine table with a high moment of inertia.
The transposition of the mating test piece relative to the workpiece can be determined directly with the aid of a displacement transducer. A direct measuring sensor or an inductive measurement sensor have proved particularly suitable.
Alternatively, the transposition can be derived indirectly from one or more suitable measurement variables. The named deviations of the rotational transmission indirectly generate a variation in the engaging force on the mating test piece in a specific direction, i.e., either leading or trailing. The mating test piece optionally undergoes a variation in the applied force which acts parallel to the axial direction of the test object. Accordingly, the required transposition can be determined from the measured force variation and information can be given on the transmission uniformity of the gear pair.
The measurement of the force variation expediently takes place via a load cell, in particular a pressure load cell, fastened to the special arbor. The mating test piece is in this respect expediently in engagement with the workpiece to be measured in a spring-loaded manner so that induced force variations of the force acting in the spring direction can be detected by the pressure load cell.
If the mating test piece is mounted at the working arbor of the gear cutting machine, the force acting on the mating test piece is alternatively determined with reference to the required positional regulation torque. The addressed positional regulation of the gear cutting machine is usually necessary to regulate a corresponding machine axis in its position relative to the workpiece center. A statement can be made on the applied forces or the force directions in the axial direction of the matching test piece with reference to the torque of the responsible axial drive applied due to the regulation. Information on pitch fluctuations in particular results.
A combination of the two methods in accordance with the present disclosure presented is generally permissible to achieve a redundant measurement procedure and measured value evaluation.
It may be expedient in a supplementary method step before the method performance to move the outer diameter of the mounted mating test piece toward a provided reference surface of the gear cutting machine. Thermal machine influences which falsify an exact positional determination of the mating test pieces can be compensated by the movement toward the reference surface. A compensation of the thermal influences is also possible by the use of a test collar at the mating test pattern. An alternative which is equally conceivable would be the use of a measuring sensor.
In an advantageous embodiment of the method in accordance with the present disclosure, the tooth space width of the workpiece is determined via the mounted mating test piece before the driving of the workpiece. The mating test piece is shifted tangentially to the workpiece until a tooth contact between the workpiece and the mating test piece can be determined. The path width of this linear movement is an indication of the tooth space width. Alternatively, the workpiece is rotated relative to the mating test piece up to tooth contact. A statement on the tooth space width can likewise be made with reference to the angle of rotation covered.
A conclusion on tooth space width can in particular be made by evaluation of the positional regulation parameters of the shift axis of the mating test piece or of the axis of rotation of the workpiece.
The rotational flank play of the gear pair in accordance with DIN 3975 is expediently determined by rotation of the mating test piece about its drive axis of rotation in both rotational directions up to flank contact. The rotational play is optionally derived using the read out positional regulation parameters of the corresponding machine axis.
To avoid any lifting of the tooth flank of the mating test piece from the tooth flank of the workpiece during the driving of the workpiece by the mating test piece, the application of a small braking torque onto the workpiece is expedient. The required braking torque is optionally effected by the machine table drive.
At least one value characterizing the rolling gear deviation of the workpiece corresponds to the standardized single-flank rolling gear deviation for gear pairs in accordance with the standards VDI/VDE 2608, DIN 3960. The single-flank rolling gear deviation is the fluctuation of the actual rotational position with respect to the reference rotational position or the fluctuation of the force variation. It results as the difference of the largest leading and the largest trailing rotational position deviation or force deviation with respect to an initial value within a revolution of the workpiece to be tested.
Alternatively or additionally, at least one value characterizing the rolling gear deviation of the workpiece corresponds to the single-flank tooth-to-tooth error. The tooth-to-tooth error is the maximum difference which occurs on the rotational position deviations within a rotational angle corresponding to the duration of a tooth engagement. The tooth-to-tooth error can be calculated analogously from the detected force deviation.
There is also the possibility that at least one value characterizing the rolling gear deviation of the workpiece is the longwave portion and/or the shortwave portion of the single-flank rolling gear deviation. The longwave portion is determined from the test image obtained in the single-flank rolling gear test by calculation and drawing a “polyline creating a mean” in which the shortwave portions are suppressed.
The shortwave portions result from the differences between the recorded test image line and the “polyline creating a mean”. The frequency per wheel circumference of the shortwave portions normally coincides with the tooth number of the workpiece to be tested. These portions can, however, also contain the influences of waviness portions in the shape deviations of section lines or flank lines.
The determination of the values optionally takes place by software control.
The output of at least one of the calculated values takes place visually, in particular graphically, by a display unit of the gear cutting machine, such as a monitor. It can be expedient for a later statistical evaluation within mass production to archive one or more values characterizing the rolling gear deviation of the workpiece.
Additional information can be acquired in the measurement of the workpiece from a contact pattern test. A contact pattern test of the workpiece to be checked can be carried out as a subsequent method step by coloring a flank of the mating test piece with marker color, in particular engineer's blue. The evaluation of the contact pattern taken can take place either manually by the machine operator or in an automated manner by an image processing system of the gear cutting machine. The coloring optionally takes place manually by the machine operator, but can also take place by an automated additional method step within the gear cutting machine.
In a preferred embodiment of the method in accordance with the present disclosure, the influence of a possible correction of the tool pivot angle on the contact pattern can be checked by modification of the pivot angle of the mating test piece during the contact pattern test/rolling gear test.
A fully automated tool change within the gear cutting machine is possible to allow the measurement of the produced workpiece within the gear cutting machine to run without human intervention. The processing tool, in particular a cutter, is replaced with a mating test piece. After the method in accordance with the present disclosure has been carried out, the mating test piece is removed again and is replaced with the required tool. This is in particular sensible when the evaluation of the values characterizing the rolling gear deviation of the workpiece makes a reworking of the workpiece necessary.
In this connection, the method in accordance with the present disclosure can put forward at least one proposal for a required reworking of the measured workpiece. After selection or confirmation of one or more correction proposals, the reworking is carried out in an automated manner within the gear cutting machine. The gear cutting machine can generally select the best proposal itself and can carry it out independently.
The present disclosure relates to an alternative method of testing a workpiece belonging to a gear pair, wherein the gear pair is either a worm gear or a cylindrical gear pair. In accordance with the present disclosure, a contact pattern test is carried out subsequent to the manufacturing process of the workpiece on the gear cutting machine producing the workpiece.
The workpiece previously had to be clamped into an external measuring machine for the contact pattern test with known gear cutting machines. If the contact pattern image shows an insufficient result of the workpiece with respect to the quality standard, a return of the workpiece to the gear cutting machine for rework is necessary. These method steps, which have to be carried out manually, are repeated for so long until a satisfactory production result is achieved.
The method in accordance with the present disclosure simplifies and accelerates the above-addressed production and test by a multiple. The machine operator machines the workpiece, for example the gear wheel, prepares the contact pattern on the gear cutting machine and can optionally simulate the influence on the contact pattern by modifications of the machine settings and can subsequently immediately recut the workpiece (worm wheel) with the amended setting parameters after the replacement of the test worm with the gear cutting tool. The total procedure of unclamping/measuring/reclamping is now limited to the measuring cycle on the gear cutting machine. Consequently, no clamping errors due to the reclamping occur either. This can result in a higher production quality.
The present disclosure further relates to a gear cutting machine for machining and measuring a workpiece, in particular for machining and measuring a worm wheel/worm and/or cylindrical gear, having a device for carrying out the methods described herein.
The gear cutting machine in accordance with the present disclosure optionally includes the required drive units for carrying out the corresponding movements of the mating test piece and of the workpiece respectively as well as expediently corresponding drive regulations which allow a recording of the required measured value parameters. The gear cutting machine furthermore provides a calculation device in the form of an electronic control unit which performs a control of the machine axes in accordance with the method and calculated at least one value which characterizes the rolling gear deviation of the clamped and measured workpiece in dependence on the recorded measurement parameters. For example, the electronic control unit may include non-transitory computer readable media include code or instructions for carrying out the method steps as described herein based on data determined from sensor coupled in the gear cutting machine and coupled to the control unit, for example. Devices, in particular a suitable loading apparatus such as a ring loader, are furthermore provided which permit a reversible automatic change between tool and mating test piece. Devices, such as the control unit, are furthermore present for carrying out a contact pattern test of the workpiece to be tested in the gear cutting machine. The devices serve the preparation of the contact pattern and, optionally, the automatic checking or evaluation of the prepared contact pattern.
Provision can be made for the measurement of the transposition of the mating test piece relative to the workpiece and of the forces acting parallel to the axis of rotation of the mating test piece that at least one displacement transducer and/or at least one spring package as well as at least one pressure load cell are arranged on or at the tool arbor taking up the mating test piece. This allows a spring-loaded bringing into engagement of the mating test piece with the tool workpiece to be measured, whereby force fluctuations which occur can be detected by the mounted pressure load cell. Devices, such as sensors, are further optionally provided which record the detected transposition or the detected pressure fluctuations or force fluctuations and forward them to the control unit. The measured values allow a conclusion on the tool transposition or test piece transposition due to defects on the counter wheel. Suitable displacement transducers are optionally direct measuring sensors, inductive measurement sensors, etc.
Further advantages and particulars of the present disclosure will be explained in detail in the following with reference to an embodiment shown in the drawings.